Simulating Terahertz Plasma Oscillations in Transistors

Terahertz plasma oscillations in GaN HEMTs are simulated in a TCAD environment using the Fermi kinetics transport model. Parallels are drawn between the Boltzmann transport equation and the shallow water dynamics used in previous studies to explain the oscillations. The necessary simulation conditions needed to observe the oscillations in a TCAD environment are described. Further discussion on the significance of the average momentum relaxation time and the rationale for choosing its value are presented. Transient simulations of THz oscillations are demonstrated when the gate voltage is perturbed at the quiescent point. A physical theory of plasma oscillations is proposed by analyzing the oscillations of the channel electron concentration, electron temperature and electric field. The electron temperature and electric field profiles are observed to be out of phase with each other, alluding to the fact that the energy is exchanged back and forth between the hot electrons and the EM fields, leading to the excitation of plasma oscillations.